Illinois Attorney General Lisa Madigan is seeking to bar a Houston-based electricity supplier from the Illinois market in a lawsuit accusing the firm of fraud and deceptive practices.

Sperian Energy, the target of the complaint, has sold power in the Chicago market for five years. The company had about 9,000 household customers here as of April, according to the complaint, filed Aug. 24 in Cook County Circuit Court. Since 2012, Sperian has served about 62,000 Chicago-area customers, the lawsuit said.

In the lawsuit, Madigan's office accused Sperian of deceiving households into paying more for electricity than they would have if they'd remained with Commonwealth Edison. The company reaches consumers mainly via telemarketers.

Calls promising savings instead resulted in contracts that in the aggregate had Sperian customers paying $12.7 million than they would have with ComEd since 2012, according to the complaint.

"Sperian's deception is an egregious example of an alternative electric supplier duping customers into believing they will save money when instead they needlessly pay more," Madigan said in a release.

An email to the media contact listed on Sperian's website bounced back. A call to her went to a voice-mail box that was full.

Madigan's complaint seeks to revoke Sperian's license to operate in Illinois, have all its residential contracts rescinded and compel it to make restitution to customers who paid too much. She also seeks penalties of $50,000 for each deceptive act.

Sperian is just one of about 50 power suppliers seeking business from households in ComEd's service territory. The industry has proved problematic in recent years as low overall power prices have made it increasingly difficult to offer savings.

Households in Northern Illinois paid $152 million more in the aggregate for electricity in the year that ended in May 2017 than they would have with ComEd, the Illinois Commerce Commission found. That was by far the most consumers have overpaid in the six years since the residential power market here effectively opened up.

Interestingly, though, Sperian isn't one of the worst-rated suppliers on the ICC's five-star system that measures customer complaints against a firm's market share. Sperian is currently a three-star supplier.

In the year that ended March 2017, Sperian was the subject of 17 complaints to the ICC. The year before that there were 36 complaints about Sperian.